Spatially Controlled Permeability and Stiffness in Photopatterned Two-Stage Reactive Polymer Films for Enhanced CO₂ Barrier and Mechanical Toughness

Controlling the microstructure of heterogeneous, polymer membranes used in gas barrier and gas separation technologies is challenging. Being able to control composite structures is beneficial to achieve an optimum combination of gas permeation and mechanical performance. In addition, unique properties such as anisotropy and confined transport can be controlled by tailoring the size and position of constituent materials. Two-stage reactive polymer (TSRP) networks are an emerging dual-cure polymer material for spatially varying cross-linking density via photopatterning. In this work a thiol-acrylate-based TSRP was used to investigate the effects of pattern geometry on CO2 permeability and mechanical properties. Line and square patterns of alternating high and low cross-linking density, with characteristic dimension between 1 mm and 10 μm, were generated in TSRP membranes. Notably, synergistic enhanced barrier properties were observed for 10 μm square patterns of lower cross-linking density (or higher permeability) material exhibiting two confined dimensions compared to line gratings with only one confined dimension.